As one type of plasma processing apparatus for subjecting workpieces, such as semiconductor wafers and the like, to plasma processing, there has been known a slot antenna-type plasma processing apparatus for generating plasma by introducing a microwave into a processing container using a planar antenna having a plurality of slots. As another plasma processing apparatus, there has been known an ICP (Inductively Coupled Plasma)-type plasma processing apparatus for generating plasma by introducing a high frequency into a processing container using a coil shaped antenna. These plasma processing apparatuses can generate dense plasma in the processing container, and oxidation, nitridation, deposition, etching and so on may be performed by the generated plasma.
For the purpose of developing next-generation devices, in order to improve productivity while coping with 3D device processing and miniaturization, there is a need to enlarge a wafer currently having a diameter of 300 mm into a wafer having a diameter of 450 mm while securing uniformity of processing in a wafer plane. Therefore, there is a need to uniformalize distribution (density distribution) of plasma in a processing container to be enlarged in response to the enlarged wafer.
In the slot antenna-type microwave plasma processing apparatus, the plasma distribution is controlled based on the shape and arrangement of slots, design of shapes of a processing container and a microwave introduction window, and so on. For example, in order to change the plasma distribution based on content of processing, there is a need to use a planar antenna having different slot shapes and arrangements which are optimally adjusted. In addition, in the above-mentioned ICP-type plasma processing apparatus, in order to change the plasma distribution, there is a need to employ an antenna having different coil shapes and arrangements which are optimally adjusted. However, such antenna replacement is a big operation which requires much time and effort such as redesign and the like.
In addition, the plasma distribution can be adjusted to an optimal plasma environment by changing process parameters such as microwave power, processing pressure, gas flow rate and the like. However, since these process parameters cannot be separated from process conditions, a width (margin) of change of the plasma distribution within a range of which the process parameters can be changed is small, thereby limiting its effects.
In addition, due to various factors such as manufacturing tolerances and assembly errors of a planar antenna, a processing container and the like, variations between devices having the same specification, and so on, symmetry of plasma in the processing container may be collapsed and the plasma distribution may be eccentric. In this case, since there is no means for correcting this in a simple method, there are difficulties in large-scaled device modification such as replacement of the planar antenna.
Therefore, in order to make the plasma distribution in the processing container more uniform, a plasma processing apparatus for introducing a microwave into different locations in the processing container and controlling a distribution of multiple plasmas generated by the microwave may be considered. In such a plasma processing apparatus, it is required to install a plurality of (for example, 7) microwave introduction modules for introducing the microwave into the processing container.
However, in the plasma processing apparatus, there is a need to detect various malfunctions occurring after the start of operation. Patent Document 1 (JP 2002-305182 A) discloses a method of determining a malfunction of a plasma status by monitoring a voltage applied to a lower electrode in a plasma processing apparatus for supplying power to the lower electrode installed in a vacuum chamber for plasma generation. Patent Document 2 (JP 2004-119179 A) discloses a method of checking a malfunction of a plasma processing apparatus by monitoring a voltage or the like on a power feed circuit in the plasma processing apparatus in which power is supplied from two high frequency power supplies having different output frequencies.
In addition, like the plasma processing apparatus in which a plurality of microwave introduction modules is installed, in the case of an apparatus in which a plurality of incident waves and reflected waves exist, it can be considered that S-parameters indicating a relationship between the plurality of incident waves and the plurality of reflected waves are used as parameters indicating the state of this apparatus. Patent Document 3 (JP 2006-317448 A) discloses that two-port S-parameter calibration is performed in power calibration of a vector network analyzer.
In the plasma processing apparatus in which a plurality of microwave introduction modules is installed, there is a need to introduce a microwave with a good balance between the plurality of microwave introduction modules. However, if a malfunction occurs in one or more of the microwave introduction modules, the balance between the plurality of microwave introduction modules is collapsed, which may result in abnormal plasma processing. Therefore, there is a need to detect a malfunction in microwave introduction modules which collapses the balance between the plurality of microwave introduction modules in such a plasma processing apparatus.